On machines for conditioning packets of cigarettes, the finished packets of cigarettes are wrapped in an overwrapping, normally comprising a sheet of polypropylene, to protect the cigarettes from the atmosphere. The sheets are formed from a strip of polypropylene, which is unwound of a reel and guided to a cutting station upstream from a folding station, and are cut off the strip, which is held taut by supporting and guide elements, as the strip is fed forward.
Given the extremely high output rate, and hence high strip consumption, of modern cigarette conditioning machines, these are equipped with automatic reel-change and strip splicing devices.
The reel-change device provides for replacing the running-out reel with a new one, and the splicing device for joining the strip on the new reel to that of the running-out reel and so ensuring continuity between the strips on the two reels without interrupting the wrapping work on the machine, which, pending splicing of the strips, is supplied by a strip store downstream from the splicing device.
Splicing the strips involves cutting the strip on the running-out reel and a surplus strip portion on the new reel by means of respective cutters, the respective blades of which are brought into contact with the respective strips and with respective counterblades.
Though satisfactory, splicing devices of the above type are structurally complex on account of the blades and respective counterblades. In addition to which, the blades require frequent sharpening and, consequently, frequent adjustment of the position of the blades with respect to the counterblades.